Answer
$\frac{12}{11}$
Work Step by Step
Currently there are $2\cdot \frac{32}{33}=\frac{64}{33}$ gallons of gasoline and $2\cdot \frac{1}{33}=\frac{2}{33}$ gallons of oil.
Thus if we want the oil to be $\frac{1}{50+1}$ of the whole mixture, then: $\dfrac{\frac{2}{33}}{\frac{2}{33}+\frac{64}{33}+x}=\frac{1}{51}\\\dfrac{\frac{2}{33}}{2+x}=\frac{1}{51}\\\frac{102}{33}=2+x\\x=\frac{36}{33}=\frac{12}{11}$
